Compositions and weatherable multilayer articles comprising resorcinol arylate chain members are known. See Published Patent Application Nos. EP 1124878 and WO0069945. The prior art references generally discuss methods to manufacture multilayer articles by various processes including co-injection molding, coextrusion, overmolding, multi-shot injection molding, sheet molding and placement of a film of the coating layer material on the surface of a substrate layer optionally followed by adhesion of the two layers by a tie-layer, with the coating layer comprising resorcinol arylate polyester chain members. In some applications, the multilayer article as taught in the prior art may be separated into the constituent substrate layer and the coating layer comprising resorcinol arylate chain members. If applied onto a substrate, i.e., wood, metal, plastic, paper, etc. as a protective carrier/weatherable layer, the inter-layers or intra-layers in the prior art may undergo separation.
Thermoset plastics are commonly used for automotive body panels including appearance parts, having to undergo extensive surface preparation to provide a weatherable, smooth, glossy surface, which always requires a coating of some type. Producing the desired surface is expensive and time consuming and detracts from the excellent mechanical properties of the thermoset materials. Without the proper finishing work a painted surface will not meet the automotive class “A” requirements due to imperfections in the surface from exposed glass fibers, glass fiber “read-through,” “paint popping,” long and short term waviness, “orange peel,” and variations in gloss. Overmolding of thin, preformed paint films is also possible, but only for compositions that are capable of being molded to provide nearly perfect surfaces without secondary operations. The as-molded surface quality has been improved considerably over the last few years, but all parts to be painted still have to be sanded, especially at the edges, and sealed and primed prior to painting. In-mold coating can obviate these operations, but only at the cost of greatly increased cycle time and cost. The process uses expensive paint systems that may be applied to the part surface while the mold is re-opened slightly, then closed to distribute and cure the coating. Surface improvements have also been obtained by the addition of low profile additives. Such additives reduce the “read-through” at the surface by causing minute internal voids due to the high stresses in the resin as it shrinks due to polymerization and differential shrinkage of the glass and resin as the part cools. The voiding of the additive relieves the stresses and provides a smoother surface. If the void occurs at the surface however, a defect may result in the finish. The voids also act as stress concentrators, which may cause premature failures under additional stress or appear during the general sanding at the surface and leave a pit that the painting process can't hide.
One alternate approach in the prior art is to adhere a thin, high quality surface film to the molded part during or after the molding operation, also known as in-mold decorating or over-molding. Such films are generally highly crosslinked films based on acrylics or fluoropolymer films, which are very expensive and need special adhesive layers, adding cost and additional sources for defects and failure. The films are generally thin due to the expense of the fluoropolymer, or brittleness if acrylic and their method of production. The thin layers also make it difficult to maintain a uniform color when the film is non-uniformly stretched to conform to the part.
Applicants have found that substrate comprising resorcinol arylate chain members may be use as a weatherable surface with high gloss and hardness, providing a class “A” finish in thermoset molding, for use in automotive parts. Applicants have also found that the use of certain tie-layers surprisingly increase the adhesion between layers of a multilayer article, with a coating layer comprising resorcinol arylate chain members and the substrate layer, or the adhesion between the multilayer article comprising a coating layer of resorcinol arylate chain members and a substrate layer with another surface. We have also found that the adhesion between the layers can be significantly improved by various surface modification methods, by modifying the surface of at least one of the layers in a multilayer article.